Considerable volumes of hydrocarbons are currently stored in natural subterranean earth intervals in porous formations of extremely low permeability, many of which are thousands of feet beneath the earth's surface. Such are generally termed “unconventional reservoirs” and may include tight (gas or oil) reservoirs, shale gas, shale oil, or coalbed methane (“CBM”) reservoirs. Unconventional reservoirs are typically stimulated for efficient or effective production.
One method of stimulating unconventional reservoirs is accomplished via hydraulic fracturing (or “fracking” or “hydrofracking” as the terms are understood by persons of ordinary skill in the art of drilling operations). Generally, fracking includes drilling a deviated well into an interval, and creating one or more hydraulic transverse fractures in the interval along the well. Once fracturing is achieved, the well may be put on production.
A problem encountered in fracking unconventional reservoirs includes the fast depletion of a completed well. Various factors contribute to this problem. One factor includes the original in-situ stress of an interval, which typically dictates fracture development making the fracturing process difficult to control. For example, induced fractures tend to propagate along the minimum stress direction of a target interval, meaning that fractures may propagate upward and perforate geological layers above a targeted interval resulting in a loss of stimulation efficiency of the interval and/or possible leakage of hydrocarbons and/or fracturing fluids into upper non-targeted interval(s). Another factor includes the low recovery of fracturing fluids injected into an interval, i.e., the low flow back ratio of fracturing fluid injected into an interval. Depending on the permeability, porosity, fluid viscosity and fracturing pressure of an interval, some of the injected fracturing fluid may remain in the fractured network of the interval resulting in less than fifty percent (<50%) recovery of the fracturing fluids. The unrecovered fracturing fluids may plug up the interval lowering the surface availability for hydrocarbon production.
Improved productivity of hydraulically fractured deviated wells is desired.